From f58a5313139536d1ea7adf9d721ebb9f923ad4c9 Mon Sep 17 00:00:00 2001
From: Juston Li <juston.li@intel.com>
Date: Thu, 19 Aug 2021 11:48:34 -0700
Subject: drm/i915/hdcp: read RxInfo once when reading
 RepeaterAuth_Send_ReceiverID_List
Git-commit: 0f317ebb5f7cb2b1d9a538c9795962fabd6e180e
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

When reading RepeaterAuth_Send_ReceiverID_List, RxInfo is read by itself
once to retrieve the DEVICE_COUNT to calculate the size of the
ReceiverID list then read a second time as a part of reading ReceiverID
list.

On some MST docking stations, RxInfo can only be read after the RxStatus
READY bit is set otherwise the read will return -EIO. The spec states that
the READY bit should be cleared as soon as RxInfo has been read.

In this case, the first RxInfo read succeeds but after the READY bit is
cleared, the second read fails.

Fix it by reading RxInfo once and storing it before reading the rest of
RepeaterAuth_Send_ReceiverID_List once we know the size.

Modify get_receiver_id_list_size() to read and store RxInfo in the
message buffer and also parse DEVICE_COUNT so we know the size of
RepeaterAuth_Send_ReceiverID_List.

Afterwards, retrieve the rest of the message at the offset for
seq_num_V.

Changes in v5:
- Don't change the offset define for Send_ReceiverID_List
  When reading, update message offset to account for RxInfo being read

Changes in v4:
- rebase and edit commit message

Changes in v3:
- remove comment

Changes in v2:
- remove unnecessary moving of drm_i915_private from patch 1

Signed-off-by: Juston Li <juston.li@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Tested-by: Suraj K <suraj.kandpal@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819184835.1181323-3-juston.li@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 31 ++++++++++----------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
index 1d0096654776..fbfb3c4d16bb 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
@@ -496,11 +496,10 @@ get_rxinfo_hdcp_1_dev_downstream(struct intel_digital_port *dig_port, bool *hdcp
 }
 
 static
-ssize_t get_receiver_id_list_size(struct intel_digital_port *dig_port)
+ssize_t get_receiver_id_list_rx_info(struct intel_digital_port *dig_port, u32 *dev_cnt, u8 *byte)
 {
-	u8 rx_info[HDCP_2_2_RXINFO_LEN];
-	u32 dev_cnt;
 	ssize_t ret;
+	u8 *rx_info = byte;
 
 	ret = drm_dp_dpcd_read(&dig_port->dp.aux,
 			       DP_HDCP_2_2_REG_RXINFO_OFFSET,
@@ -508,15 +507,11 @@ ssize_t get_receiver_id_list_size(struct intel_digital_port *dig_port)
 	if (ret != HDCP_2_2_RXINFO_LEN)
 		return ret >= 0 ? -EIO : ret;
 
-	dev_cnt = (HDCP_2_2_DEV_COUNT_HI(rx_info[0]) << 4 |
+	*dev_cnt = (HDCP_2_2_DEV_COUNT_HI(rx_info[0]) << 4 |
 		   HDCP_2_2_DEV_COUNT_LO(rx_info[1]));
 
-	if (dev_cnt > HDCP_2_2_MAX_DEVICE_COUNT)
-		dev_cnt = HDCP_2_2_MAX_DEVICE_COUNT;
-
-	ret = sizeof(struct hdcp2_rep_send_receiverid_list) -
-		HDCP_2_2_RECEIVER_IDS_MAX_LEN +
-		(dev_cnt * HDCP_2_2_RECEIVER_ID_LEN);
+	if (*dev_cnt > HDCP_2_2_MAX_DEVICE_COUNT)
+		*dev_cnt = HDCP_2_2_MAX_DEVICE_COUNT;
 
 	return ret;
 }
@@ -534,6 +529,7 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 	const struct hdcp2_dp_msg_data *hdcp2_msg_data;
 	ktime_t msg_end = ktime_set(0, 0);
 	bool msg_expired;
+	u32 dev_cnt;
 
 	hdcp2_msg_data = get_hdcp2_dp_msg_data(msg_id);
 	if (!hdcp2_msg_data)
@@ -546,17 +542,22 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 
 	hdcp->cp_irq_count_cached = atomic_read(&hdcp->cp_irq_count);
 
+	/* DP adaptation msgs has no msg_id */
+	byte++;
+
 	if (msg_id == HDCP_2_2_REP_SEND_RECVID_LIST) {
-		ret = get_receiver_id_list_size(dig_port);
+		ret = get_receiver_id_list_rx_info(dig_port, &dev_cnt, byte);
 		if (ret < 0)
 			return ret;
 
-		size = ret;
+		byte += ret;
+		size = sizeof(struct hdcp2_rep_send_receiverid_list) -
+		HDCP_2_2_RXINFO_LEN - HDCP_2_2_RECEIVER_IDS_MAX_LEN +
+		(dev_cnt * HDCP_2_2_RECEIVER_ID_LEN);
+		offset += HDCP_2_2_RXINFO_LEN;
 	}
-	bytes_to_recv = size - 1;
 
-	/* DP adaptation msgs has no msg_id */
-	byte++;
+	bytes_to_recv = size - 1;
 
 	while (bytes_to_recv) {
 		len = bytes_to_recv > DP_AUX_MAX_PAYLOAD_BYTES ?
-- 
2.38.1